SBWvc: DLcosb-3EQ measured from the whole sample was slightly lower in smokers (Table 1). DI was significantly increased in smokers (Table 1; P<0.05) and correlated with age in smokers (r =0.48; P<0.001) but not in nonsmokers, and with pack-years of smoking (r =0.55; P<.001) (Figure 6). However, there were no differences between smokers and nonsmokers for either Sn or Emix (Table 1) as previously reported . Furthermore, Di did not correlate with Sn in either smokers or nonsmokers. The day-to-day coefficient of variation of Di for this manoeuvre was 1.6±5.9% in 10 normal subjects who repeated the manoeuvre on five successive days .
Figure 5) The reduction in degree of diffusion nonuniformity (Di) from 0 s to 10 s of breath holding (ADi) for submaximal single breath washout (SBWsm) (y axis) correlates with the change in normalized phase III helium slope (Sn)from 0 to 10 s of breath holding (ASn) for SBWsm manoeuvres in both smokers (r2=0.51, P<0.001, solid line) and nonsmokers (r2=0.31, P<0.01, dashed line). O Nonsmokers; 0 Smokers
Figure 6) For vital capacity single breath washout manoeuvres degree of diffusion nonuniformity (Di) correlates with pack-years of smoking (left diagram) in smokers (r2=0.55, P<0.001) and with age in smokers (r2=0.48, P<0.01) but not in nonsmokers (right diagram). O Nonsmokers; l Smokers; yr Years